2009-06-18_GENERAL DOCUMENTS - C1981018

Home Browse Search

The operator has committed to a program of visual monitoring to identify subsidence caused damage to surface structures, stock ponds, and major damages, and has committed to repair hazardous tension cracks, subsidence features interrupting flow in Red Wash or Scullion Gulch, or damage to surface structures. Subsequent monitoring and observation have largely verified initial subsidence impact projections. Current and future monitoring includes daily monitoring of County Road 65 while mining below the road and during the active subsidence periods and twice-weekly monitoring of Scullion Gulch and stock ponds during periods of undermining. XVI. Concurrent Surface and Underground Mining No specific approvals are granted to the applicant under this section. XVII. Operations on Alluvial Valley Floors The permit area and adjacent lands contain three stream channels - the White River, Red Wash, and Scullion Gulch - with enough associated alluvium to be considered as potential alluvial valley floors. All three channels cross the permit area as well as adjacent area. The permittee's alluvial valley floor analysis is contained in Section II.D of Vol. 2 of the permit application. Below is a detailed consideration of the alluvial valley floor potential of each of the following three drainages: Red Wash, Scullion Gulch and the White River. Red Wash Water Availability Criteria - Artificial Flood Irrigation The permittee estimated the potential average annual water yield from Red Wash drainage basin using Grunsky's Formula (Grunsky 1908, Sellars, 1965; see bibliography in permit application). The estimate indicates that an average of 2,090 acre feet of water could be made available annually in Red Wash. This corresponds to approximately 0.32 inches of runoff, which is about 3.5 percent of the annual precipitation falling on the area. Actual measurements of flow on Red Wash have been made using a crest stage gage station located at the mouth of the basin. With the crest stage gage approach towards stream monitoring, only peak flows that occur between monitoring intervals are recorded. Flows that occur at less than peak flow during any one monitoring interval will not be recorded. The crest gage method is, therefore, useful for recording peak events only; the method has limited application for determining duration of flow, and consequently for flow volumes which occur during the monitoring interval. The results of the crest gage monitoring efforts on Red Wash indicate that flow is almost entirely in response to snowmelt and storm rainfall events. A total of six runoff events were recorded during the two year inventory period conducted by the permittee. Events Deserado Mine 41 June 18, 2009